RFC3966 Format (tel: Links)

RFC 3966 defines the "tel" URI scheme — the format behind every click-to-call link on the web. A global tel URI is the E.164 number with visual separators allowed: tel:+1-415-555-0132. Tapping it on a phone opens the dialer with the number pre-filled.

Click-to-call matters for mobile SEO and conversion: more than half of web traffic is mobile, and a tappable number removes every step between reading and calling. Google also reads tel: links as a business-contact signal.

The URI accepts parameters — tel:+15551234567;ext=89 encodes an extension — and RFC 3966 requires globally routable numbers to use the + country-code form, never national format. tel:0207946... breaks for every visitor outside the UK.

tel: URI Syntax

  • Scheme prefix tel: followed by the number in + country-code form.
  • Visual separators (hyphens, dots) are permitted: tel:+44-7400-123456.
  • Extensions encode as a parameter: tel:+15551234567;ext=89.
  • Spaces are not allowed anywhere in the URI.
  • Defined by IETF RFC 3966 (2004), which replaced RFC 2806.

Ready-Made tel: Links for 10 Countries

The same numbers from our country guides, written in RFC3966 format:

CountryRFC3966 example
🇺🇸 United States (+1) tel:+1-415-555-0132
🇬🇧 United Kingdom (+44) tel:+44-7400-123456
🇨🇦 Canada (+1) tel:+1-416-555-0199
🇦🇺 Australia (+61) tel:+61-491-570-156
🇮🇳 India (+91) tel:+91-98765-43210
🇩🇪 Germany (+49) tel:+49-1512-3456789
🇫🇷 France (+33) tel:+33-6-12-34-56-78
🇪🇸 Spain (+34) tel:+34-612-34-56-78
🇮🇹 Italy (+39) tel:+39-312-345-6789
🇧🇷 Brazil (+55) tel:+55-11-91234-5678

Click-to-Call Use Cases

  • Click-to-call links on websites: <a href="tel:+14155550132">.
  • Email signatures and HTML newsletters.
  • vCard / contact files and QR codes that trigger dialing.
  • Schema.org telephone properties in structured data.

Building tel: Links

HTML click-to-call
<a href="tel:+14155550132">Call us: +1 415 555 0132</a>
<!-- Display text can be pretty; the href must be RFC3966. -->
JavaScript (libphonenumber-js)
import { parsePhoneNumber } from 'libphonenumber-js';

const phone = parsePhoneNumber('+14155550132');
phone.format('RFC3966'); // 'tel:+1-415-555-0132'
With an extension
tel:+15551234567;ext=89
// RFC3966 parameter syntax — most mobile dialers
// will prompt to dial the extension after connecting.

Generate a tel: Link

Drop in any phone number and copy a standards-compliant RFC3966 tel: URI for your website, signature or vCard.

Enter phone number with country code or select country below.

Try:

RFC3966 and tel: Links FAQ

What is RFC3966 format?

The IETF standard for "tel" URIs — phone numbers as links. Format: tel: plus the E.164 number, with optional hyphens: tel:+1-415-555-0132. It powers click-to-call on every smartphone.

How do I make a phone number clickable in HTML?

Wrap it in an anchor with a tel: href: <a href="tel:+14155550132">+1 415 555 0132</a>. Always use the international + form in the href so the link works for visitors abroad.

Can tel: links include extensions?

Yes — RFC3966 defines an ext parameter: tel:+15551234567;ext=89. Support varies by device; iOS and Android dialers generally handle it.

Should tel: links use spaces?

No. Spaces are invalid inside a URI. Use hyphens or nothing: tel:+14155550132 or tel:+1-415-555-0132 are both valid; "tel:+1 415..." is not.

Other Formats